In Canada the mowing season is short, and both ends of it matter. The first mow sets up a lawn that has spent months under snow, and the last mow decides whether it comes out matted and patchy next April.
When should you mow for the first time in spring?
When three signals line up:
- The grass is growing. Green is not enough. It should be clearly taller than a week ago.
- It is about one and a half times your mowing height. For a lawn kept at 7 cm, around 10 cm.
- The ground is firm. If your boots sink or leave wet prints after the thaw, the mower will leave ruts.
In southern Ontario that is usually late April or early May, earlier on the West Coast and later on the Prairies. Grass gets going once the soil holds above about 8 to 10°C.
How should the first mow be done?
Rake matted patches and clear the debris the snowbanks left behind, then start with a sharp blade. Set the deck at your summer height or one notch higher and only take off the tips. Scalping a lawn that has just greened up slows it down for weeks. Bag the clippings the first time if there is a lot of dead grass, and mulch from then on.
When should you stop mowing in the fall?
When the grass stops growing, not when the trees drop their leaves. Bluegrass keeps growing through October and often into November, long after the maples are bare. Keep mowing on the one-third rule while it grows. Growth usually ends after a few hard frosts in late October or November, depending on the year and where you live.
Leaves have to come off before the snow. A mulching mower handles a light layer, but a thick mat of maple leaves under snow is a recipe for dead patches.
How short should the lawn go into winter?
About 5 to 6 cm for Kentucky bluegrass, a little higher for tall fescue. Bring it down over the last two or three mows, never more than a third at a time. Long grass flattens under the snow and holds moisture against the crowns, which is where snow mold starts. A scalped lawn loses the leaf that insulates it.
What does the app show for a Toronto lawn?
The example bluegrass lawn in Toronto has a 6.5 cm target. Browse the calendar forward to November and the mowing card shows the step down for winter:
In November the app lowers bluegrass to its winter floor of 5 cm, with October halfway there at about 5.8 cm. Tall fescue has a 6.4 cm floor, and ryegrass and fine fescue stay at their normal height. Every two weeks around midday matches slow late-fall growth and gives the frost time to melt.
Spring is where you need your own judgement. For March the calendar shows weekly mowing at 6.5 cm. The app uses one schedule for the band between roughly the 35th and 50th parallel, from Tennessee to southern Ontario, so for Toronto its February and March suggestions are too early. Use the card for the height and wait for the three signals above.
What should you do after the last mow?
- Clean the deck. Wet clippings left over winter rust the deck.
- Sharpen the blade now. One job less in spring.
- Run the fuel out or add stabilizer. Stale gas is the most common reason a mower will not start in April.
- Mark the lawn edges. Stakes along the driveway help the snowplow and the shovel miss the grass.
The last fertilizer of the year goes on around the time of the last mows. The timing is in When to Fertilize Your Lawn in Canada, and the height for the rest of the season is in How Short to Mow Grass in Canada. What a Green Lawn keeps the height for each month in its calendar, so you do not have to remember the winter height next fall.